Conventional mobile devices include a diverse collection of services in a single embedded system. These services may include cellular phone calling, general-purpose processing, audio and video encoding and decoding, 3-D graphics, Wi-Fi and Internet access, and/or GPS tracking. Future mobile device manufactures will likely add more features to extend offered services and remain competitive.
Certain services may need protection from unauthorized access, either from another component of the system or from external debugging access (i.e., JTAG). This protection is especially important for audio and video devices that operate on data protected by digital rights management (DRM). Authorized components in the chip decrypt data internally for processing or playback, but the system must hide this decrypted data from other components lacking DRM protection.
Mobile applications are written by a variety of sources (e.g., open-source hobbyists to professional software development companies) and are frequently executed on a single device. Invariably, some applications are vulnerable to hijacking by third-parties.
It would be desirable to implement an application to share one or more ATT mapping tables with hijacked clients, but prevent hijacked clients from extending control into a privileged area by preventing hijacking of the ATT tables.